1. Field of the Invention
The present invention relates to an ink jet recording head performing recording by discharging ink and a manufacturing method thereof.
2. Description of the Related Art
The ink jet recording systems disclosed in U.S. Pat. Nos. 4,723,129 and 4,740,796 can perform high-speed, high-density, high-accuracy, high-image-quality recording, and are suitable for colorization and compactification. A recording head that uses the ink jet recording systems to bubble ink using thermal energy for discharging the bubbled ink onto a recording medium is generally configured as follows. That is, the configuration is one in which a heating resistor for bubbling the ink and wiring to perform electric connection to the heating resistor are produced on the same substrate to use the substrate as a substrate for an ink jet recording head and further nozzles for discharging the ink are formed over the substrate.
On the other hand, various methods have been proposed as to the formation method and the material of the nozzles. One of the representative ones is the method of forming liquid chambers, discharge ports and supply ports by resin molding in advance to directly stick the molded member to the substrate. Another method is to form through-holes in the substrate to use the through-holes as supply ports, and to form the liquid chambers, the wall members of the liquid chambers and the discharge ports on the substrate using a resin by the photolithographic method so that the liquid chambers, the wall members and the discharge ports communicate with the supply ports. The latter method can perform the high-density arrangement of the discharge ports in comparison with the former method, and the latter method is presently the most popular method accordingly.
The method of forming the components of the recording head using a resin by the photolithographic method as described above is simple in manufacturing, but the method causes the following problems pertaining to the reliability thereof.
1. Because the linear expansion coefficients of the resin and the substrate, which is an inorganic material, differ from each other, the resin easily peels off from the substrate at the interface between them.
2. The resin absorbs moisture to swell, and the dimensional accuracy thereof becomes worse consequently.
Accordingly, in order to overcome the problems mentioned above, devices of changing the resin material to an inorganic material have been made.
For example, there have been proposed the method of coating an inorganic material on a substrate to form the members by the photolithographic method, and the method of forming the members by the chemical vapor deposition (hereinafter simply referred to as “CVD”).
The materials used for the formation of the CVD are denser than the materials used for the coating method, and are good in the resistance property and the like to ink. Consequently, the former materials are suitable for the wall members of the liquid chambers and the material of the discharge port portions, but the CVD includes the following problems caused by the property thereof.
For example, if the following process is performed, the flow paths are completed. That is, a material to become the shapes of flow paths is formed on a substrate; an inorganic material to coat the shapes is formed by the CVD after that; discharge ports for discharging ink are then formed in the inorganic material; and the shapes are removed.
However, because a film formed by the CVD grows along the substrate and the shape material unlike the growth of the films formed by the spin coat method and the like, a dent on a groove is formed between the wall members of each flow path. Then, the thicker the thickness of the shape material (corresponding to the heights of the ink flow paths) is, the deeper the grooves become. Consequently, when ink adheres to the grooves at the time of ink discharging, or at the time of cleaning the discharge ports of a head, the adherence exerts a bad influence upon the discharge of ink.
Moreover, also the following problem exists. That is, when the wall members of the liquid chambers are formed, it is better to thicken the thickness of the film made to grow by the CVD in order to give the film a certain measure of strength. However, when the film formed on the shape material is too thick, the thicknesses of the discharge ports become too thick when the discharge ports are formed. Consequently, a problem is caused in the discharge performance in turn.
The present invention was made in consideration of the problems mentioned above. The present invention provides an ink jet recording head that settles the problem of the grooves between the walls of the ink flow paths which problem is caused when the wall members of the ink flow paths are made of an inorganic material, and that includes a flattened discharge port surface. Moreover, the present invention provides an ink jet recording head equipped with the wall members of ink flow paths that have a sufficient mechanical strength.